The invention relates to a light emitting diode (LED), and more particularly to a LED with molding unit and fabrication method thereof.
Multi-chip LEDs comprise a plurality of different color light emitting chips. The most common white multi-chip LED is a RGB LED. RGB LEDs comprise red (R), green (G) and blue (B) light emitting chips for obtaining white light.
FIG. 1 shows a bullet type RGB LED structure. Red light emitting chip R, green light emitting chip G and blue light emitting B are disposed in the lead frame 10. The sidewalls of lead frame 10 comprise a highly reflective layer with a curvature for condensing the light emitted from the light emitting chips R, G and B. This type of LED further comprises lens type molding unit 12 to improve directionality thereof. A RGB LED has a good color mixing, the one would not see different color at different viewing angle. The light emitting chips R, G and B are positioned in different positions in the lead frame 10, however, the color-mixing effect of the bullet type LED is reduced. The lens type molding unit 12 reduces the color-mixing effect.
FIG. 2 shows a surface-mount device (SMD) RGB LED structure. The SMD RGB LED has no lens type molding unit, so its directionality is worse than the bullet type RGB LED. Furthermore, the surface of the lead frame 20 of the SMD RGB LED is uneven, thus the color-mixing effect and color uniformity are improved. At the same time, the uneven surface reflects and even scatters light, both of which decrease the SMD RGB LED directionality. In short, the SMD RGB LED improves color-mixing but reduces directionality.
Thus, the bullet type LED has good directionality, but bad color-mixing; the SMD type LED has bad directionality, but good color-mixing. Hence, there is a need for a LED with good directionality and good color-mixing characteristics.